// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2012 Désiré Nuentsa-Wakam <desire.nuentsa_wakam@inria.fr>
// Copyright (C) 2012 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef SPARSELU_KERNEL_BMOD_H
#define SPARSELU_KERNEL_BMOD_H

namespace Eigen {
namespace internal {

template<int SegSizeAtCompileTime>
struct LU_kernel_bmod
{
	/** \internal
	 * \brief Performs numeric block updates from a given supernode to a single column
	 *
	 * \param segsize Size of the segment (and blocks ) to use for updates
	 * \param[in,out] dense Packed values of the original matrix
	 * \param tempv temporary vector to use for updates
	 * \param lusup array containing the supernodes
	 * \param lda Leading dimension in the supernode
	 * \param nrow Number of rows in the rectangular part of the supernode
	 * \param lsub compressed row subscripts of supernodes
	 * \param lptr pointer to the first column of the current supernode in lsub
	 * \param no_zeros Number of nonzeros elements before the diagonal part of the supernode
	 */
	template<typename BlockScalarVector, typename ScalarVector, typename IndexVector>
	static EIGEN_DONT_INLINE void run(const Index segsize,
									  BlockScalarVector& dense,
									  ScalarVector& tempv,
									  ScalarVector& lusup,
									  Index& luptr,
									  const Index lda,
									  const Index nrow,
									  IndexVector& lsub,
									  const Index lptr,
									  const Index no_zeros);
};

template<int SegSizeAtCompileTime>
template<typename BlockScalarVector, typename ScalarVector, typename IndexVector>
EIGEN_DONT_INLINE void
LU_kernel_bmod<SegSizeAtCompileTime>::run(const Index segsize,
										  BlockScalarVector& dense,
										  ScalarVector& tempv,
										  ScalarVector& lusup,
										  Index& luptr,
										  const Index lda,
										  const Index nrow,
										  IndexVector& lsub,
										  const Index lptr,
										  const Index no_zeros)
{
	typedef typename ScalarVector::Scalar Scalar;
	// First, copy U[*,j] segment from dense(*) to tempv(*)
	// The result of triangular solve is in tempv[*];
	// The result of matric-vector update is in dense[*]
	Index isub = lptr + no_zeros;
	Index i;
	Index irow;
	for (i = 0; i < ((SegSizeAtCompileTime == Dynamic) ? segsize : SegSizeAtCompileTime); i++) {
		irow = lsub(isub);
		tempv(i) = dense(irow);
		++isub;
	}
	// Dense triangular solve -- start effective triangle
	luptr += lda * no_zeros + no_zeros;
	// Form Eigen matrix and vector
	Map<Matrix<Scalar, SegSizeAtCompileTime, SegSizeAtCompileTime, ColMajor>, 0, OuterStride<>> A(
		&(lusup.data()[luptr]), segsize, segsize, OuterStride<>(lda));
	Map<Matrix<Scalar, SegSizeAtCompileTime, 1>> u(tempv.data(), segsize);

	u = A.template triangularView<UnitLower>().solve(u);

	// Dense matrix-vector product y <-- B*x
	luptr += segsize;
	const Index PacketSize = internal::packet_traits<Scalar>::size;
	Index ldl = internal::first_multiple(nrow, PacketSize);
	Map<Matrix<Scalar, Dynamic, SegSizeAtCompileTime, ColMajor>, 0, OuterStride<>> B(
		&(lusup.data()[luptr]), nrow, segsize, OuterStride<>(lda));
	Index aligned_offset = internal::first_default_aligned(tempv.data() + segsize, PacketSize);
	Index aligned_with_B_offset = (PacketSize - internal::first_default_aligned(B.data(), PacketSize)) % PacketSize;
	Map<Matrix<Scalar, Dynamic, 1>, 0, OuterStride<>> l(
		tempv.data() + segsize + aligned_offset + aligned_with_B_offset, nrow, OuterStride<>(ldl));

	l.setZero();
	internal::sparselu_gemm<Scalar>(
		l.rows(), l.cols(), B.cols(), B.data(), B.outerStride(), u.data(), u.outerStride(), l.data(), l.outerStride());

	// Scatter tempv[] into SPA dense[] as a temporary storage
	isub = lptr + no_zeros;
	for (i = 0; i < ((SegSizeAtCompileTime == Dynamic) ? segsize : SegSizeAtCompileTime); i++) {
		irow = lsub(isub++);
		dense(irow) = tempv(i);
	}

	// Scatter l into SPA dense[]
	for (i = 0; i < nrow; i++) {
		irow = lsub(isub++);
		dense(irow) -= l(i);
	}
}

template<>
struct LU_kernel_bmod<1>
{
	template<typename BlockScalarVector, typename ScalarVector, typename IndexVector>
	static EIGEN_DONT_INLINE void run(const Index /*segsize*/,
									  BlockScalarVector& dense,
									  ScalarVector& /*tempv*/,
									  ScalarVector& lusup,
									  Index& luptr,
									  const Index lda,
									  const Index nrow,
									  IndexVector& lsub,
									  const Index lptr,
									  const Index no_zeros);
};

template<typename BlockScalarVector, typename ScalarVector, typename IndexVector>
EIGEN_DONT_INLINE void
LU_kernel_bmod<1>::run(const Index /*segsize*/,
					   BlockScalarVector& dense,
					   ScalarVector& /*tempv*/,
					   ScalarVector& lusup,
					   Index& luptr,
					   const Index lda,
					   const Index nrow,
					   IndexVector& lsub,
					   const Index lptr,
					   const Index no_zeros)
{
	typedef typename ScalarVector::Scalar Scalar;
	typedef typename IndexVector::Scalar StorageIndex;
	Scalar f = dense(lsub(lptr + no_zeros));
	luptr += lda * no_zeros + no_zeros + 1;
	const Scalar* a(lusup.data() + luptr);
	const StorageIndex* irow(lsub.data() + lptr + no_zeros + 1);
	Index i = 0;
	for (; i + 1 < nrow; i += 2) {
		Index i0 = *(irow++);
		Index i1 = *(irow++);
		Scalar a0 = *(a++);
		Scalar a1 = *(a++);
		Scalar d0 = dense.coeff(i0);
		Scalar d1 = dense.coeff(i1);
		d0 -= f * a0;
		d1 -= f * a1;
		dense.coeffRef(i0) = d0;
		dense.coeffRef(i1) = d1;
	}
	if (i < nrow)
		dense.coeffRef(*(irow++)) -= f * *(a++);
}

} // end namespace internal

} // end namespace Eigen
#endif // SPARSELU_KERNEL_BMOD_H
